具張或壓應力CESL應變矽nMOSFET之特性分析與熱載子效應

Performance and Hot-Carrier Effect of Strained nMOSFETs with Tensile and Compressive CESL Stressors

李冠徵(Kuan-Cheng Li)

指導教授 ： 黃恆盛 ； 陳雙源

國立臺北科技大學/機電學院/機電整合研究所/碩士(2011年)

https://doi.org/10.6841/NTUT.2011.00052

摘要

CESL(接觸蝕刻停止層)應變技術，主要是藉由電晶體上沉積不同比例的氮化矽薄膜，利用所產生的張或壓應力，來間接使通道上的應力改變，提升載子遷移率，以達到增強電晶體的效能。
雖然已有文獻探討在不同CESL應變技術下對於nMOSFET效能的影響，但很少有對結合雙軸應變與CESL應變技術來進行探討。因此在本篇論文中，我們研究具有張或壓應力CESL在結合雙軸應變後，對於不同閘極長度下nMOSFET的效能影響，以及分析短通道時的熱載子效應。
隨著通道長度的縮短，藉由CESL技術對通道產生的應力，再結合雙軸應變的影響後，確實可讓通道拉伸的效果增加，因而提高nMOSFET的汲極電流，而具有壓應力CESL的nMOSFET，汲極電流也能有所改善。
本研究也針對具有不同CESL應變的nMOSFET進行了熱載子效應的可靠度測試，並推導其使用壽命模式及計算介面狀態(interface state)和氧化層陷入電荷(oxide trapped charge)的變化量。從實驗結果發現，具有CESL應變的元件，熱載子效應的劣化情況會比傳統元件要來得嚴重，推測與沉積不同比例的氮化矽薄膜有關係，因為在製程時，較容易會有額外的原子往通道區域擴散，經過熱載子效應的可靠度測試後，造成介面產生大量的缺陷，不論是室溫或高溫下，具有壓應力CESL的元件，劣化的程度都會最為嚴重。

關鍵字

應變矽 ； 接觸蝕刻停止層 ； 熱載子效應

並列摘要

CESL stressor, a kind of uniaxial strained-Si technology, is to deposit SiN layer on the MOSFETs. The device performance can be improved due to the mechanical strain produced by the SiN capping layer.
From previous literatures, CESL stressor with biaxial strained-Si technology has not been clearly investigated. This work studies the impact of the CESL stressors with biaxial strained-Si in terms of different lengths for 90 nm nMOSFETs and explores the channel-hot-carrier (CHC) effect in short channel nMOSFETs.
For short channel nMOSFETs, the tensile strain in channel is more effectively produced from tensile CESL stressors. Hence, it is evidenced from our experiment that the tensile CESL stressors with biaxial strained-Si have increased the drain current of the nMOSFETs. In addition, the increment of the drain current for compressive CESL stressors has been revealed.
The reliability of CHC with various CESL stressors for the nMOSFETs also investigated. Moreover, their lifetimes are calculated, and the increments of interface states and oxide trapped charges based on CHC stress are analyzed. Comparing with the control devices, we discover that nMOSFETs with the CESL stressors and biaxial strained-Si exhibit more degradation than control devices, so the degradation has a close relationship with SiN film. It is presumable that the hydrogen species are generated during the SiN deposition process, and they may diffuse toward channel region, resulting in large number of defects in the interface. For the temperature effects, no matter low or high, the degradation of nMOSFETs with compressive CESL stressors is more serious than nMOSFETs with tensile CESL stressors.

並列關鍵字

Strained-Si ； contact-etch-stop-layer(CESL) ； hot-carrier effect

參考文獻

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